The control of individual operations of multi-operational systems such as a robot or machine tool by adding set increments of action (i.e. movement, velocity, etc.) for each action to obtain desired action per unit time of each controlled element is known. In general the tasks to be carried out at each controlled axis are divided into a series of discrete positions or steps and the commands passed to the axis controls at a constant rate. In some systems this procedure, normally called interpolation, is carried out in two stages by defining the series of positions for all axes and then fine stage interpolation is carried out at each axis control and coordination of the axes is maintained to ensure the desired path of action is attained. It is also known to compare the desired action of a given axis with the actual action at that point in time and the difference between these two, used to determine a multiplication factor that is applied to control this axis. The greater the difference, the greater multiplication factor applied to adjust that axis thereby causing the slower axis to operate more rapidly to catch up to the faster axes. With this control system, each individual axis is self-regulated but the overall control of the system may not remain synchronized.
U.S. Pat. No. 5,222,017 issued Jun. 22, 1993 Yellowley et al. describes a control system for synchronizing slaves (slave computers each controlling an axis of a multi-operation system) using synchronizing pulses sent simultaneously to all the slaves in the system to time their operations and ensure that all the slaves remain in a preselected relationship by only adding increments of change to each slave when all of the slaves attain their then current desired operating state.
The system described in the Yellowley et al. patent is an effective control for multiple slave operations to ensure they retain their synchronization (relative relationship by operating the overall system on the basis of the slowest operating parameter with no means for increasing the operating rate when all slaves are operating below their maximum acceptable levels.